1. Field of the Invention
The present invention relates generally to methods of manufacture of flexible energy absorbing structures, and more specifically to a novel resilient, flexible, fusion bonded, honeycombed panel incorporating thermoplastic elastomer materials or the like and the method of manufacturing such apparatus.
2. Brief Description of the Prior Art
It is well known that honeycombed panels have heretofore been provided consisting of an array of hexagonal cells made of strips of flat material glue bonded together and nested so that each wall of one cell is shared with walls of adjacent cells to provide a structure which, depending upon the type of materials used, can vary between being quite rigid on the one hand and being flexible on the other. See for example, the U.S. patents to Barut U.S. Pat. No. 3,018,205, Eakin et al U.S. Pat. No. 3,556,917, and Kennedy et al U.S. Pat. No. 3,483,070. Whereas structures of the former type are suitable for making lightweight panels for use in walls, aircraft structures, boat hull structures, and other configurations where rigidity, strength and light weight characteristics are important, when crushed these structures exhibit little if any recovery and are thus permanently degraded. In structures of the latter type wherein the honeycombed material is flexible a cushioning structure can be provided which is resilient and energy absorbing.
Applications for the resilient structures are many and varied, as disclosed in the U.S. patents to Holland U.S. Pat. No. 2,887,425 Landi et al U.S. Pat. Nos. 4,422,183, and 4,485,568. As is pointed out in these patents, one way to manufacture a resilient honeycombed structure is to place a number of sheets or ribbons of flexible material in side-by-side relation, bonding them together intermittently using a vulcanization process or suitable adhesives. After the sheets are bonded together, the assembly is then severed to form core stacks of ribbons or strips intermittently bonded together at staggered intervals along the length of the strips. The thus bonded strips are then expanded in a lateral direction to create a honeycombed core to which layers of material are adhesively bonded to both faces of the core to form a structural unit.
Although such units are, in fact, superior to prior structures, they are expensive and difficult to manufacture in quantity due to complexities associated with the vulcanization and/or adhesive bonding and assembly techniques required. In addition, such structures suffer from other disadvantages including (1) poor bonding between core and facing materials; (2) core node failures after repetitive impacts or compressions; (3) limitations as to compatibility between materials used for core, facings and adhesives; (4) cosmetic degeneration of transparent facing materials caused by adhesive solvents; and perhaps most importantly, (5) the hazards associated with the use of the combustible and toxic adhesive solvents.